Water Budgets and River Regimes Flashcards
What are water budgets?
water budgets show the balance between precipitation, evaporation and runoff in an area throughout a year. They can be useful to show the availability of water for agricultural, domestic and industrial use throughout the year.
They are calculated using this formula:
P = Q + E ± S
Where:
P = precipitation
Q = Discharge
E = evaporation
S = changes in storage
Periods and components of a water budget
Soil moisture surplus - Precipitation exceeds potential evapotranspiration. Soils become saturated and further infiltration cannot occur.
Soil moisture utilisation - An increase in transpiration means plants absorb more water from their roots. Evapotranspiration rates begin to exceed precipitation
Soil moisture deficit - All available water in the soil gas been used. Typically during this period the ground becomes baked.
Soil moisture recharge -Precipitation levels increase and evapotranspiration rates drop. this allows the pores of the spoil to refill with water.
What are river regimes?
River regimes show the annual variation in discharge of a river at a particular point. They vary from place to place due to the size of the river, the amount pattern and intensity of rainfall, temperature, geology, vegetation and human activity. Different areas will therefore have very different river regimes. For example in Oceanic Europe (I.E the UK) discharge is highest in the Winter and lower in the Summer due to more rainfall in inter and higher evapotranspiration in Summer. Whereas in glacial or mountainous areas, glacier melt snowmelt in the summer causes discharge to be greater in the summer months.
What is a storm hydrograph ?
Storm hydrographs show the variation is river discharge following a storm event. they can be ‘flashy’ - characterised by a short lag time, with a high peak discharge and steep rising limb - o rhtey can be ‘subdued’ - characterised by long lag time, a low peak discharge and a gentle sloping rising limb.
Characteristics of a storm hydrograph
Rising limb - Shows the increase in river discharge following a storm event
Lag time - the time between peak rainfall and peak discharge
Falling limb - Shows the decrease in river discharge
Baseflow: the normal discharge of a river
factors affecting storm hydrographs
Climate
Geology
Soils
Relief
Basin size
shape
Vegetation
Human activity
drainage intensity ( E.G number of streams)
